So much for the essential facts of this very singular story. Unless we dismiss it all as the ingenious fabrication of Mr. Wace, we have to believe one of two things: either that Mr. Cave's crystal was in two worlds at once, and that while it was carried about in one, it remained stationary in the other, which seems altogether absurd; or else that it had some peculiar relation of sympathy with another and exactly similar crystal in this other world, so that what was seen in the interior of the one in this world was, under suitable conditions, visible to an observer in the corresponding crystal in the other world; and _vice versa_. At present, indeed, we do not know of any way in which two crystals could so come _en rapport_, but nowadays we know enough to understand that the thing is not altogether impossible. This view of the crystals as _en rapport_ was the supposition that occurred to Mr. Wace, and to me at least it seems extremely plausible... And where was this other world? On this, also, the alert intelligence of Mr. Wace speedily threw light. After sunset, the sky darkened rapidly-- there was a very brief twilight interval indeed--and the stars shone out. They were recognisably the same as those we see, arranged in the same constellations. Mr. Cave recognised the Bear, the Pleiades, Aldebaran, and Sirius; so that the other world must be somewhere in the solar system, and, at the utmost, only a few hundreds of millions of miles from our own. Following up this clue, Mr. Wace learned that the midnight sky was a darker blue even than our midwinter sky, and that the sun seemed a little smaller. _And there were two small moons!_ "like our moon but smaller, and quite differently marked," one of which moved so rapidly that its motion was clearly visible as one regarded it. These moons were never high in the sky, but vanished as they rose: that is, every time they revolved they were eclipsed because they were so near their primary planet. And all this answers quite completely, although Mr. Cave did not know it, to what must be the condition of things on Mars. Indeed, it seems an exceedingly plausible conclusion that peering into this crystal Mr. Cave did actually see the planet Mars and its inhabitants. And if that be the case, then the evening star that shone so brilliantly in the sky of that distant vision was neither more nor less than our own familiar earth.